package hihocoder;
import java.util.Scanner;

/**
 * 
 */

/**计算F1值，注意为0的情况
 * @author zhongfang
 *
 */
public class F1值 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		int N=scanner.nextInt();
		int TPcount=0;
		int Tcount=0;
		int Pcount=0;
		scanner.nextLine();
		for (int i = 0; i < N; i++) {
			String string=scanner.nextLine();
			char x=string.charAt(0);
			char y=string.charAt(2);
			if(x=='+'){
				Tcount++;
			}
			if(y=='+'){
				Pcount++;
			}
			if(x=='+'&&y=='+'){
				TPcount++;
			}
		}
		double p=0;
		double r=0;
		double f=0;
		if(TPcount!=0){
			p=(double)TPcount/Tcount;
			r=(double)TPcount/Pcount;
			f=200*p*r/(p+r);
		}
		System.out.println(String.format("%.2f", f)+"%");
	}
}
